John T. Vessey

Using significance tests to evaluate equivalence between two experimental groups.

Equivalency testing, a statistical method often used in biostatistics to determine the equivalence of 2 experimental drugs, is introduced to social scientists. Examples of equivalency testing are offered, and the usefulness of the method to the social scientist is discussed.

The role of disease-specific infectivity and number of disease exposures on long-term effectiveness of the latex Condom

Background Condom use is a primary prevention strategy for sexually transmitted infections (STIs). Consistent condom use substantially reduces the risk of HIV infection. Similar levels of effectiveness for reducing the risk of other STIs have not been established. Differences in disease-specific infectivity and the number of exposures to an infected partner may explain differences in condom effectiveness. Goal The goal was to examine the impact of differing infectivities and increasing numbers of exposures on theoretical condom effectiveness. Study Design Mathematical modeling using estimated disease-specific infectivities and condom failure rates. Results Condom effectiveness decreases as disease-specific infectivity and the number of exposures to infection risk increase. Conclusions Condom effectiveness for decreasing STI risk is influenced by disease infectivity and the number of exposures. Generalizations from studies of relatively uninfectious STIs to highly infectious STIs or from short-term studies to longer-term situations will overestimate condom effectiveness.

The Psychotherapeutic Service Delivery System

We can understand the relevance of psychotherapy research for clinical practice only by considering the broader context of the psychotherapy service delivery system. Epidemiologic studies of the incidence and prevalence of emotional disturbance provide estimates of the need for services; surveys of providers and their practice patterns yield estimates of available resources to meet those needs; and studies of patient characteristics and patterns of psychotherapy utilization identify the constituencies served by the psychotherapy delivery system. From these data we know that each person in need of mental health services has available no more than an average of three treatment sessions from a mental health professional in any given year. Despite the fact that a small proportion of such individuals actually seek service, each such individual who consults the speciality mental health sector has available no more than an average of 10 treatment sessions. The most needy, particularly those lacking in education,...